This project is designed to study the anatomy and physiology of oxytocin pathways in the brain of the rat. Immunocytochemical methods are being used on the light and electron-microscopic level to localize pathways producing this peptide. The oxytocin system is now known to be very complex and extensive including pathways to other neurons in forebrain, brainstem and spinal cord. Influences of these and other pathways on the milk-ejection reflex are under study including actions of the endorphins, substance P and other peptides, acetyl choline and catecholamines. Other studies concern the roles of oxytocin in the paraventricular nucleus (PVN) of the hypothalamus compared to the supraoptic nucleus. Bilaterals lesions are being made in PVN to establish its contribution to milk-ejection and to extrahypothalamic projections.